Various types of tensioners have been devised for use in the oil and gas industry. U.S. Pat. No. 4,039,177 discloses a compensation mechanism with a passive damped pneumatic-hydraulic spring system. U.S. Pat. No. 4,799,827 discloses a modular riser tensioner, and U.S. Pat. No. 5,160,219 discloses a variable spring rate riser tensioner. U.S. Pat. No. 4,617,998 discloses a riser with a braking system. Other patents of interest includes U.S. Pat. Nos. 3,970,292, 4,004,532, 4,072,190, 4,215,950, 4,616,707, 4,721,053, 4,799,827, 4,828,230, 4,883,387, 4,883,388, 4,892,444, 5,020,942, 5,252,004, 5,283,552, 5,244,313, 5,551,803, 5,671,812, 5,846,028, 5,944,111, 6,045,296, 6,585,455, 7,112,011, 7,328,741, 7,329,070, and 7,632,044.
U.S. Pat. No. 4,787,778 discloses a riser tensioning system with three tensioners pivotally secured to a hollow surface of the production platform and to a tensioner ring. Publications of interest include U.S. 2005/0147473, U.S. 2006/0108121, U.S. 2006/0280560, U.S. 2007/0056739, U.S. 2007/0196182, U.S. 2008/0205992, and U.S. 2009/0145611.
The disadvantages of the prior art are overcome by the present invention, an improved riser tensioning system is hereinafter disclosed.